[HTML][HTML] Trophic slime, allergic slime

M Wills-Karp - American journal of respiratory cell and molecular …, 2000 - atsjournals.org
American journal of respiratory cell and molecular biology, 2000atsjournals.org
The epithelium of the respiratory mucosa provides a barrier against injurious luminal agents,
including bacteria, enzymes, and toxins. The normal respiratory epithelium is coated with
mucus, which provides a variety of protective functions, including protection of the lower
airways from dehydration and from damaging airborne irritants, particles, and
microorganisms. The adhesive and viscoelastic properties of mucus glycoproteins (mucins),
the major protein components of airway mucus, allow the trapping of foreign substances and …
The epithelium of the respiratory mucosa provides a barrier against injurious luminal agents, including bacteria, enzymes, and toxins. The normal respiratory epithelium is coated with mucus, which provides a variety of protective functions, including protection of the lower airways from dehydration and from damaging airborne irritants, particles, and microorganisms. The adhesive and viscoelastic properties of mucus glycoproteins (mucins), the major protein components of airway mucus, allow the trapping of foreign substances and their transport and removal on the tips of beating cilia toward the throat, a process termed mucociliary clearance. However, overzealous production of mucus may significantly contribute to the morbidity and mortality associated with certain respiratory diseases. In particular, mucus hypersecretion and plugging of the airways are characteristic features of patients who die from asthma (1, 2), chronic bronchitis, and cystic fibrosis (2). In human airways, mucins are produced and secreted by specialized cells in the epithelium, including the goblet cells in the surface airway epithelium and the secretory (mucous and serous) cells in the submucosal glands. Because of their greater prominence in histologic sections, submucosal glands, rather than goblet cells, have been thought to contribute the greater quantity of mucus to airway surface fluid (3). However, recent studies suggest that goblet cells may contribute more to the overall quantity of mucus produced than do the submucosal glands. Mucins constitute a heterogeneous group of high molecular weight, richly glycosylated molecules. To date, nine human mucin genes (MUC1, MUC2, MUC3, MUC4, MUC5/5AC, MUC5B, MUC6, MUC7, and MUC8) encoding the protein core of mucin have been identified (reviewed in Reference 4). The biologic importance of these diverse mucin proteins is not currently known. Nonetheless, there appears to be some degree of specificity in the tissue expression of the various MUC genes. In the respiratory tract, seven of the nine MUC genes are expressed (MUC1,
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